Lubricating oils thickened to a grease with hydrous metal salts and process for forming same



United States Patent LUBRICATING OILS THICKENED TO A GREAE WITH HYDROUSMETAL SALTS AND PROCESS FOR FORMING SAME Arnold J. Moi-way, Clark, N.1., assignor to Esso Research and Engineering Company, a corporation ofDelaware No Drawing. Application April 1, 1955 Serial No. 498,741

12 Claims. (Cl. 252-372) This invention relates to new and usefullubricating compositions and to the method of preparing the same. Moreparticularly, the invention pertains to oil-dispersible compositionsconsisting of hydrous mixtures of metal salts of low molecular weightcarboxylic acids and moderate molecular weight carboxylic acids and tosols, gels or greases containing the same.

One aspect of the present invention relates to greases or gelling agentstherefor, containing no soap and consisting of or containing a hydrousmixture of metal salts comprising at least one metal salt of lowmolecular weight carboxylic acid having from about 1 to 3 carbon atomsper molecule and at least one metal salt of moderate molecular Weightcarboxylic acid having from about 7 to 10 carbon atoms per molecule inwhich the mol ratio of low molecular weight carboxylic acid to moderatemolecular weight carboxylic acid is at least about 2 to 1. Thecompositions of the invention include novel and improved greases,lubricating oils, etc. In particular, greases containing the hydrousmixtures of metal salts of the invention as grease thickeners have beenfound to have excellent extreme pressure properties as well as otherdesirable grease characteristics.

The use of carboxylic acids in the preparation of grease thickeners iswell known in the art. Heretofore, the mixtures of carboxylic acidsemployed for such purposes have consisted of mixtures of high molecularweight carboxylic acids or combinations of high molecular weightcarboxylic acids and low molecular weight carboxylic acids in the formof metal soaps or metal soap-salt complexes. These complexes, forexample, have been prepared from the commonly known soapforming,grease-making, high molecular weight fatty acids, saturated orunsaturated, containing from 12 to 22 carbon atoms, and low molecularweight carboxylic acids having from 1 to 6 carbonatoms such as acetic,propionic, alkoxy propionic, furoic and the like. Normally aboutequimolar proportions of these low and high molecular Weight carboxylicacids have been employed by the prior art in the preparation of themetal soap-salt complexes. Highly desirable characteristics recentlyhave been imparted to these types of complex compounds by drasticallyincreasing the low molecular weight acid content, and with it the metalcontent, of the soap-salt complexes, so that they contain at least 7moles and up to 40 moles or more of the low molecular weight acid permol of the high molecular weight acid. These complex compounds have beenprepared at temperatures of about 450 to 550 F.

The present invention isbased on the surprising discovery that hydrousmixtures of metal salts alone, prepared at temperatures of about 150 to200 F. and comprising a metal salt of low molecular Weight carboxylicacid, a metal salt of moderate molecular weight carboxylic acid andwater, canbe effectively employed as lubricating grease thickeners,which impart to' the final grease compositions outstanding extremepressure properties. It has also been found that a mol ratio of above2,303,847 Patented Dec. 9, 1958 Egg The low molecular weight acidscontemplated in this invention include saturated and unsaturatedcarboxylic acids having from about 1 to 3 carbon atoms, such as formic,acetic, propionic, acrylic, and lactic acid. Acetic acid is especiallypreferred. Mixed low molecular weight carboxylic acids wherein the acidscontain from about 1 to 3 carbon atoms and have an averagesaponification value of above about 540 may also be employed.

The intermediate molecular weight acids are those aliphaticmonocarboxylic acids containing from about 7 to 10 carbon atoms,preferably about 8 to 9 carbon atoms. Either saturated or unsaturatedfatty acids may be utilized, though the saturated fatty acids arepreferred. Straight chain or substantially straight chain acids are alsopreferred. The average saponification value of the single or mixedintermediate molecular weight acids should be about 310 to 440,preferably about 350 to 420. Some of the intermediate molecular weightmonocarboxylic acids coming within the above prescriptions areexemplified by:

5-methyl-2-hexanoic Heptanoic (enanthic) Octanoic (caprylic) 2-ethylhexanoic C Oxo acids Nonanoic (pelargonic) Decanoic (capric) C Oxo acidsCommercial mixtures of these intermediiate molecular weight carboxylicacids having an average saponification value of from about 310 to 440can also be employed.

The Oxo acids useful for the purposes of the present invention, e. g.the saturated branched chain C and C Oxo acids, can be prepared by meansof the well known Oxo synthesis. This process involves the oxonation orcarbonylation of olefins with carbon monoxide and hydrogen attemperatures of about 300 to 400 F. and pressures of about 2500 to 4000p. s. i. g. in the presence of a group VIII metal catalyst, preferablycobalt. In U. S. Patent No. 2,632,021 the Oxo process and the nature ofthe reaction products, e. g. the C OX0 products, are disclosed indetail. The preparation of 0x0 acids from the OX0 reaction products isdescribed in U. S. Patent No. 2,537,577 and U. S. Patent No. 2,553,364.Neither the preparation of the 0x0 reaction products nor the preparationof OX0 acids therefrom are considered to be directly related to theessence of the present invention. The C and C 0x0 acids may be derivedrespectively from C and C olefins obtained by polymerizing propylenealone or with some butylene.

The choice of the metal component depends to a certain extent on use forwhich the hydrous mixture of metal salts of the invention iscontemplated. The alkaline earth metals, particularly calcium, areespecially useful for many purposes of the invention. These metalsafford greatest advantages when the hydrous mixtures of their salts areused as thickeners in the manufacture of greases, because the greasescontaining them have outstanding load carrying characteristics, andstructural stability at high temperatures and under mechanical stresseven without the use of conventional extreme pressure additives andstabilizing agents. The alkaline earth metals ditler in this respectfrom the alkali metals, i. e. sodium, potassium and lithium. Hydrousmixtures of metal salts of high alkali metal content, formed from theacids and in the mol ratios of this invention, yield greases of lessstructural stability even when added to the oil dispersant in relativelyhigh proportions.

Other metals useful for the purposes of this invention are the heavymetals of groups I, II, IV and VIli of the periodic system. inparticular, metals such as copper. zinc. lead, cobalt, strontium,magnesium and cobalt can be used.

The metal components of the salts of both low and intermediate molecularweight acids may be any one or more of the metals set forth above.Though the metal of the salts may be either the same or different, inmost cases the salts contain the same metal.

The hydrous mixtures of the metal salts may be prepared byco-neutralization of a mixture of the acids with suitable bases,particularly the hydroxides and/or carbonates of the metals desired. Theco-neutralization step may be carried out in situ in the liquidmenstruum to which the mixture of salts is to be applied in actual use.For example. the mixed acids may be co-neutralized in a portion or allof the lubricating oil forming the dispersant of a grease to bethickened by the hydrous mixture of salts. This method is particularlydesirable in cases in which the salts have the same metal constituent.The temperature at which the co-neutralization is carried out will be inthe range of about 150 to 200 F. heating step is carried out in a liquiddispersant, the latter should have a boiling point above the heatingtemperature or the heating should be carried out under pressure.

The hydrous mixture of metal salts may also be prepared by separatelypreforming at least a portion of the low molecular weight earboxylicacid salt and/or the intermediate molecular weight carboxylic acid salt.This method is especially useful when different metals are employed asbases for the salt constituents. Preformed metal salts can replace about30 to 80% of the free acids and stoichiometric equivalent bases.

The choice of material to which the hydrous mixture of salts of highmetal content are applied also depends, of course. on the usecontemplated. For lubricant manufacture. the detergency and extremepressure characteristics of the hydrous mixtures of metal salts may beutilized in combination with a wide variety of mineral as well assynthetic lubricating oils. Relatively large proportions of chemicallycombined yet active metal thus may be introduced into the oils withoutsettling out. the lubricating oil should have a viscosity within therange of about 60 to 2500 SUS at 100 F. and about 35 to 200 SUS at 210F.. a pour point of about +20 to -75 F., and a flash point of about 350to 650 F. A viscosity index of 100 or higher is also usually desirable,though oils having a lower viscosity index can be employed. Aspreviously mentioned, synthetic as well as mineral lubricating oils canbe employed as part or all of the liquid phase of the grease. and theyinclude synthetic lubricat ing oils of the hydrocarbon, hydrocarbonpolymer. ester, complex ester. formal, mereaptal, polyalkylene oxide,silicone or similar types. Synthetic oils such as the simple diesters.di-Z-ethylhexyl sebacate, di-C -oxo azelate, and di-isooctyl azelate orthe complex esters formed from glycols. dicarboxylic acids and alcoholsor monocarboxvlic acids can also be used.

Hydrous metal salts mixture proportions of about 5 to 50 wt. percent.preferably about to wt. percent, ba ed on the total weight of thegrease, may be used in preparing the novel greases of this invention.For other compositions of this invention the proportion may be as low asone percent by weight or even 0.1% when the de ired effect of metalcontent is simply either catalytic as For a paint dryer oranti-corrosive as for combining with a corrosive ash upon combustion.

When this 0 In general,

The hydrous mixture of metal salts may also be prepared in a lowviscosity mineral and/or synthetic lubrieating oil and then blended withmineral and/or synthetic lubricating oils having the substantially sameor higher viscosities to produce grease compositions within the scope ofthis invention.

The temperature at which the hydrous mixture of metal salts is preparedor treated is an important feature of the present invention, since itwill determine the physical as well the chemical characteristics of theresulting prodnets. in accordance with this invention, temperatures ofabout to 200 F. preferably about to 200 R, are employed to prepare thehydrous mixtures 01' metal salts. By allowing the temperature ofreaction to rise to 212 F., some of the water of reaction can be partlyremoved. Ilowcvc this requires close control and, in general, thetemperature is held below 212 F. These temperatures are below thoserequired to dehydrate to form anhydrous mixtures or to form complexes orcompounds with coordinated valcnces from the mixtures of metal salts.Thus, the hydrous mixtures of metal salts of the invention will containthe water of reaction or the water introduced along with the reagents,c. g. aqueous solutions of the low molecular weight carboxylic acids.The amount of water present in the hydrous mix tures of metal salts canvary widely. Usually, however, about 0.5 to 15.0 wt. percent, preferably1 to 5 wt. percent, water based on the total weight of the hydrousmixture of metal salts will be present.

Another significant feature of the present invention is the high metalcontent of the hydrous mixtures of metal salts. By employing thecombination of low and intermediate molecular weight acids in accordancewith this invention, mol ratios of low to intermediate molecular weightacids of about 2:1 to about 40:1. preferably about 5:1 to 30:1, can beemployed without encountering solu bility or sedimentation problems.

The invention will be more fully understood by refcrence to thefollowing specific examples illustrating various modifications of theinvention.

EXAMPLE I A number of mineral oil base lubricating grease compositionsthickened with a hydrous mixture of the metal salts of acetic acid andcaprylic acid and having the formulations listed in Table I below wereprepared as follows:

Product A This lubricant was prepared by blending 20% of grease A with80% of a mineral lubricating oil having a viscosity of 80 SUS/ZlO" F.,i. e. the mineral oil base of grease A.

Product C This product was prepared substantially as described in thepreparation of grease A, except that the only acid employed was aceticacid.

Product D This product was prepared by blending 20% of Product C with80% of the mineral lubricating oil having a viscosity of 80 SUS/210 F.

Product E This grease was prepared substantially as described in thepreparation of grease A, except that an aqueous solutron of acetic acid,80% in concentration, was employed assess? 6 l to a fire heated kettleand warmed with stirring to 135 F. Blended acetic and capyrylic acidswere added to the mixture and the temperature rose to 212 F. briefly,while continuing stirring. An excellent, smooth uniform in place of theglacial acetic acid 5 tggilasg containing most of the water of reactionwas ob- Product F Properties This lubricant was prepared by blending 20%f Appearance Smooth, uniform grease grease E with 80% of the samemineral lubricating oil Dr pping polnt F.) 500+ having a viscosity of soSUS/210 F. 10 Penetranons F-, i /1 The composition of these products andtheir properties Unworked 2 are tabulated below in Table 1. Worked (60strokes) 210 It Will be noted that greases prepared by thickening Worked(100,000 strokes) 21? with a hydrous mixture of metal salts of low andinter- Water solubility (boiling water) N11 mediate molecular weightcarboxylic acids were stable 15 Almen test (weights carried) 6non-Settling greases havinsoutstandipg extreme Pressure This exampleillustrates that the hydrous mixtures of and antl'cormslon p p It W111b6 further HOied metal salts of the invention can be utilized incomposi- TABLE I Product A B 0 D E F Formulation:

Glacial acetic acid 1 p 200 49 Acetic acid (80%) Commercial caprylicacid (Sap. No. 327) Hydrated lime Mol ratio (acetic to caprylic acids)25.8/1 25.8/1 Appearan ca Excellent, Fluid. Smooth, Fluid. Excellent,Fluid.

Smooth, Uniform. Smooth, Uniform. Uniform. Mobilometer Consistency 77 F.815 752. Penetrations (77 F., H1I11./l0)

Unworked Worked (60 strokes) Worked (75,000 strokes) Free Alkalinity(percent N aOH) Timken Test (lbs. carried) Separates in 48 hrs.Corrosiom None Oil Separation None Separates oil Stable suspencopiouslysion after 2 on storage, weeks.

1 Consistency is product of time in seconds and load in grams requiredfor a perforated cone to sink through a fixed depth of semi-fluidsubstance.

It is a relative measure of viscosity in non-Newtonian fluids.

that substantially all of the water of reaction remains in thelubricant. Portions of the greases so prepared can also be diluted toany salt concentration by blending with additional mineral oil up to 99%or more. (See Products B and F.)

The use of acetic acid alone resulted in unsatisfactory compositionsfrom which the salt and oil separated. (See Products C and D.)

Products E and F demonstrate that large amounts of water can betolerated, and that in some lubricating services it can be distinctlybeneficial. Aqueous solutions of acetic acid, in 80% or lowerconcentrations can be employed.

The lubricating compositions of the invention as described above aresuitable, for example, as marine diesel engine upper cylinderlubricants. These compositions containing calcium salts are capable ofreducing cylinder liner wear and minimizing acid corrosion byneutralizing the acids formed during the combustion of fuels.

EXAMPLE II A grease was prepared from the following ingredients:

Formulation Weight percent 1 Methyl phenyl polysiloxanes having a highratio of phenyl to methyl groupings. Viscosity is 1060 SUS/l00 F.

Preparation All of the silicone fluid and hydrated lime were chargedtions other than mineral oils, namely in the preparation of siliconepolymer greases.

In brief summary, it has now been found that a metal salt of a lowmolecular weight carboxylic acid can be stably dispersed in lubricatingoils by a cold set method of forming a concentrated base and thenblending the base to the desired salt content by diluting withadditional lubricating oil. An intermediate molecular weight carboxylicacid is co-neutralized with the low molecular weight carboxylic acid andact as the stabilizing agent. By this method large amounts of hydrousmetal salts of low molecular weight carboxylic acids can be suspended inthe lubricating oil as a colloidal dispersion easily and inexpensively.At least some and usually all water of reaction remains in thelubricating composition.

The invention is not limited to the specific conditions and materials ofthe foregoing examples. These conditions and materials may be variedwithin the limits indicated in the general portions of thespecification. The compositions prepared in accordance with theinvention may contain various conventional additives, such as oxidationinhibitors, metal deactivators, corrosion pre ventatives, extremepressure agents, dyes, etc., as will be understood by those skilled inthe art.

What is claimed is:

1. A lubricating grease composition which comprises a lubricating oilbase stock thickened to grease consistency with from 5 to 30 weightpercent of a hydrous mixture of a metal salt of a low molecular weightmonocarboxylic acid having from about 1 to 3 carbon atoms per moleculeand a metal salt of an intermediate molecular weight monocarboxylic acidhaving from about 7 to 10 carbon atoms per molecule, in which the molratio of low to intermediate molecular weight carboxylic acids isbetween 2:] and 40:1, wherein said hydrous composition contains 0.5 to15.0 weight percent water and said metal is selected from the groupconsisting of alkali metals, alkaline earth metals and heavy metals ofgroups I, ll, IV and VIII of the periodic system.

2. A blended lubricating composition comprising a minor proportion ofthe lubricating grease composition of claim 1 and a major proportion ofa mineral lubrieating oil, Sttlcl grease composition being present insuffieient amount to improve the lubricating propgrties if said blendedlubricating composition.

3. The blended lubricating composition of claim 2 wherein l to 20 weightpercent of the lubricating grease composition of claim 1 and 99 to 80weight percent 01 said mineral lubricating oil is employed.

4. A lubricating grease composition which cuinpristm a major proportionof a lubricating oil and a minor grease-making proportion of a hydrousmixture of alkaline earth metal salts of acetic acid and caprylic acid,in which the mol ratio of acetic to caprylic acid is about 5:l to 30:1and wherein said hydrous salt mixture contains 10.5 to 15.0 Weightpercent water.

5. The lubricating grease composition of claim 4 in which saidlubricating oil is a mineral lubricating oil.

6. The lubricating grease composition of claim 4 in which saidlubricating oil is a synthetic lubricating oil.

7. The method of preparing a hydrous oil-dispersible salt compositioncontaining 0.5 to 15.0 weight percent water, in a lubricating oil whichcomprises mixing in said oil a low molecular weight monocarboxylic acidhaving l to 3 carbon atoms per molecule with an intermediate molecularweight monocarboxylic acid containing 7 to 10 carbon atoms per moleculein :1 mol ratio of low to intermediate molecular weight carboxylic acidsof at least 2:1, reacting the mixture with a metal base sufficient inamount to form metal salts of said acids at a temperature of about 150to 200 F. to thereby form a dispersion of said salts in said oil.

8. The method of claim 7 in which said base is an alkaline earth metalbase.

9. The method according to claim 8 wherein said base is hydrated lime.

10. The method of preparing a lubricating grease coiuposition whichcomprises dispersing in a lubricating oil a low molecular weightmonocarboxylic acid having from about 1 to 3 carbon atoms per molecule,an intermediate molecular weight monocarboxylic acid having from about 7to 10 carbon atoms per molecule and a metal base in grease'maltingproportions, heating the dispersion to a temperature of about 150 to 200F. and then cooling to obtain said lubricating grease composition, themol ratio of low to intermediate molecular weight acids be ing between2:1 and 40:1 and said metal being selected from the group consisting ofalkali metals, alkaline earth metals and heavy metals of groups I, ll,IV and Vlll of the periodic system.

11. The method of preparing a lubricating grease composition accordingto claim 10 wherein the lubricating oil is selected from the groupconsisting of mineral and synthetic lubricating oils.

12. The method of preparing a lubricating grease composition accordingto claim 11 wherein said synthetic lubricating oil is a silicone polymeroil.

*Xeferences Cited in the file of this patent UNITED STATES PATENTS2,274,675 Earle Mar. 3, 1942 2,274,676 Earle Mar. 3, 1942 2,384,551Jehle Sept. 11, 1945 2,487,080 Swenson Nov. 8, 1949 2,583,607 Sirianniet a1. Jan. 29, 1952 2,606,153 Holdstock Aug. 5, 1952 2,628,195 Allesonet a1. Feb. 10, 1954 2,628,202 Alleson et al. Feb. 10, 1954 2,735,815Morway et a1. Feb. 21, 1956 UNITED STATES PATENT ()FFICE fiertificatePatent No. 2,863,847 Patented December 9, 1958 ARNOLD J. MORWAYApplication having been made by Arnold J. Morway, the inventor named inthe patent above identified, Esso Research and Engineering Company, acorporation of Delaware, the assignee, Judson L. Philips of UpperMontclair, New Jersey, and John J. Kolfenhach of North Plainfield, NewJersey, for the issuance of a certificate under the provisions of Title35, Section 256 of the United States Code, adding the names of saidJudson L. Philips and John J. Kolfenbach to the patent as jointinventors, and a showing and proof of facts satisfying the requirementsof the said section having been submitted, it is this 28th day of April,1959, certified that the names of the said Judson L. Philips and John J.Kolfenbach are hereby added to the said patent as joint inventors withthe said inventor named in the patent.

[SEAL] ARTHUR W. CROCKER,

First Assistant Gommissz'oner of Patents.

1. A LURICATING GREASE COMPOSITION WHICH COMPRISES A LUBRICATING OILBASE STOCK THICKENED TO GREASE CONSISTENCY WITH FROM 5 TO 30 WEIGHTPERCENT OF A HYDROUS MIXTURE OF A METAL SALT OF A LOW MOLECULAR WEIGHTMONOCARBOXYLIC ACID HAVING FROM ABOUT 1 TO 3 CARBON ATOMS PER MOLECULEAND A METAL SALT OF AN INTERMEDIATE MOLECULAR WEIGHT MONOCARBOXYLIC ACIDHAVING FROM ABOUT 7 TO 18 CARBON ATOMS PER MOLECULE, IN WHICH THE MOLRATIO OF LOW TO INTERMEDIATE MOLECULAR WEIGHT CARBOXYLIC ACIDS ISBETWEEN 2:1 AND 40:1, WHEREIN SAID HYDROUS COMPOSITION CONTAINS 0.5 TO15.0 WEIGHT PERCENT WATER AND SAID METAL IS SELECTED FROM THE GROUPCONSISTING OF ALKALI METALS, ALKALINE EARTH METALS AND HEAVY METALS OFGROUPS I, II, IV AND VIII OF THE PERIODIC SYSTEM.